Question

A force of 40 N is required to pull up cylindrical barrel of mass 2.5 kg through a distance of 7.5 m along the inclined plane as shown in diagram alongside. Calculate.

1. Force of gravity acting on the barrel. (Take g = 10 ms⁻²)
2. Work done by the force in pulling body along the inclined plane.
3. Work done against the force of gravity.

Answer 1

(a) Force of gravity (weight) = mg

= 2.5 × 10

= 25 N

(b) Work done by the pulling force = force × distance

= 40 × 7.5

= 300 J

(c) The vertical height of the incline is h = 7.5 sin 30° = 3.75 m.

Therefore, work done against gravity = mgh

= 2.5 × 10 × 3.75

= 93.75 J